﻿#if CLUSTER
using System;
using System.Collections.Generic;
using System.Globalization;
using System.IO;
using System.Linq;
using System.Text;

namespace BookSleeve
{
    /// <summary>
    /// Represents a client that communicates to multiple redis-cluster nodes.
    /// </summary>
    [Obsolete("This API is experimental prototype and entirely subject to change; you have been warned!")]
    public partial class RedisCluster : IDisposable
    {
        [Obsolete("no no no")]
        public void SuspendFlush()
        {
            foreach (var node in nodes) node.Connection.SuspendFlush();
        }
        [Obsolete("no no no")]
        public void ResumeFlush()
        {
            foreach (var node in nodes) node.Connection.ResumeFlush();
        }

        /// <summary>
        /// Computes the hash-slot that would be used by the given key
        /// </summary>
        public static int HashSlot(string key)
        {
            return HashSlot(Encoding.UTF8.GetBytes(key));
        }
        /// <summary>
        /// Computes the hash-slot that would be used by the given key
        /// </summary>
        public static int HashSlot(byte[] key)
        {
            //HASH_SLOT = CRC16(key) mod 16384
            unchecked {
                uint crc = 0;
                for (int i = 0; i < key.Length; i++)
                        crc = ((crc<<8) ^ crc16tab[((crc>>8) ^ key[i])&0x00FF]) & 0x0000FFFF;
                return (int)(crc % 16384);
            }
        }

        /// <summary>
        /// Return the underlying connection that currently maps to a specified key
        /// </summary>
        [Obsolete("This method certainly won't be public")]
        public RedisConnection GetConnection(string key)
        {
            var slot = HashSlot(key);
            foreach (var node in nodes)
            {
                if (node.HadBucket(slot))
                {
                    RedisConnection conn = node.Connection;
                    if (conn != null && conn.State == RedisConnectionBase.ConnectionState.Open)
                    {
                        return conn;
                    }
                }   
            }
            // otherwise, pick any healthy node and await further instruction
            foreach (var node in nodes)
            {
                var conn = node.Connection;
                if (conn != null && conn.State == RedisConnectionBase.ConnectionState.Open) return conn;
            }
            throw new InvalidOperationException("No node could be resolved for hash-slot " + slot.ToString());

        }
        static readonly ushort[] crc16tab = {
            0x0000,0x1021,0x2042,0x3063,0x4084,0x50a5,0x60c6,0x70e7,
            0x8108,0x9129,0xa14a,0xb16b,0xc18c,0xd1ad,0xe1ce,0xf1ef,
            0x1231,0x0210,0x3273,0x2252,0x52b5,0x4294,0x72f7,0x62d6,
            0x9339,0x8318,0xb37b,0xa35a,0xd3bd,0xc39c,0xf3ff,0xe3de,
            0x2462,0x3443,0x0420,0x1401,0x64e6,0x74c7,0x44a4,0x5485,
            0xa56a,0xb54b,0x8528,0x9509,0xe5ee,0xf5cf,0xc5ac,0xd58d,
            0x3653,0x2672,0x1611,0x0630,0x76d7,0x66f6,0x5695,0x46b4,
            0xb75b,0xa77a,0x9719,0x8738,0xf7df,0xe7fe,0xd79d,0xc7bc,
            0x48c4,0x58e5,0x6886,0x78a7,0x0840,0x1861,0x2802,0x3823,
            0xc9cc,0xd9ed,0xe98e,0xf9af,0x8948,0x9969,0xa90a,0xb92b,
            0x5af5,0x4ad4,0x7ab7,0x6a96,0x1a71,0x0a50,0x3a33,0x2a12,
            0xdbfd,0xcbdc,0xfbbf,0xeb9e,0x9b79,0x8b58,0xbb3b,0xab1a,
            0x6ca6,0x7c87,0x4ce4,0x5cc5,0x2c22,0x3c03,0x0c60,0x1c41,
            0xedae,0xfd8f,0xcdec,0xddcd,0xad2a,0xbd0b,0x8d68,0x9d49,
            0x7e97,0x6eb6,0x5ed5,0x4ef4,0x3e13,0x2e32,0x1e51,0x0e70,
            0xff9f,0xefbe,0xdfdd,0xcffc,0xbf1b,0xaf3a,0x9f59,0x8f78,
            0x9188,0x81a9,0xb1ca,0xa1eb,0xd10c,0xc12d,0xf14e,0xe16f,
            0x1080,0x00a1,0x30c2,0x20e3,0x5004,0x4025,0x7046,0x6067,
            0x83b9,0x9398,0xa3fb,0xb3da,0xc33d,0xd31c,0xe37f,0xf35e,
            0x02b1,0x1290,0x22f3,0x32d2,0x4235,0x5214,0x6277,0x7256,
            0xb5ea,0xa5cb,0x95a8,0x8589,0xf56e,0xe54f,0xd52c,0xc50d,
            0x34e2,0x24c3,0x14a0,0x0481,0x7466,0x6447,0x5424,0x4405,
            0xa7db,0xb7fa,0x8799,0x97b8,0xe75f,0xf77e,0xc71d,0xd73c,
            0x26d3,0x36f2,0x0691,0x16b0,0x6657,0x7676,0x4615,0x5634,
            0xd94c,0xc96d,0xf90e,0xe92f,0x99c8,0x89e9,0xb98a,0xa9ab,
            0x5844,0x4865,0x7806,0x6827,0x18c0,0x08e1,0x3882,0x28a3,
            0xcb7d,0xdb5c,0xeb3f,0xfb1e,0x8bf9,0x9bd8,0xabbb,0xbb9a,
            0x4a75,0x5a54,0x6a37,0x7a16,0x0af1,0x1ad0,0x2ab3,0x3a92,
            0xfd2e,0xed0f,0xdd6c,0xcd4d,0xbdaa,0xad8b,0x9de8,0x8dc9,
            0x7c26,0x6c07,0x5c64,0x4c45,0x3ca2,0x2c83,0x1ce0,0x0cc1,
            0xef1f,0xff3e,0xcf5d,0xdf7c,0xaf9b,0xbfba,0x8fd9,0x9ff8,
            0x6e17,0x7e36,0x4e55,0x5e74,0x2e93,0x3eb2,0x0ed1,0x1ef0
        };
        /// <summary>
        /// Releases any resources associated with this object.
        /// </summary>
        public void Dispose()
        {
            // TODO: thread safety on the list enumerator
            foreach (var node in nodes)
            {
                node.Dispose();
            }
        }


        internal class ClusterNode : IDisposable
        {
            public RedisConnection Connection { get; private set; }
            public string Key { get; private set; }
            public bool HadBucket(int bucket)
            {
                foreach (var range in ranges)
                {
                    if (bucket >= range.Start && bucket <= range.End) return true;
                }
                return false;
            }
            struct Range
            {
                public readonly int Start, End;
                public Range(int start, int end) { this.Start = start; this.End = end;}
                public override string ToString()
                {
                    return Start.ToString() + "-" + End.ToString();
                }
            }
            private readonly List<Range> ranges = new List<Range>();
            public ClusterNode(string key, RedisConnection connection, string ranges)
            {
                Key = key;
                this.Connection = connection;
                var candidateRanges = ranges.Split(',');
                this.ranges = new List<Range>(candidateRanges.Length);
                foreach (var range in candidateRanges)
                {
                    var pair = range.Split('-');
                    int start, end;
                    if (pair.Length != 2 || !int.TryParse(pair[0], NumberStyles.Any, CultureInfo.InvariantCulture, out start)
                        || !int.TryParse(pair[1], NumberStyles.Any, CultureInfo.InvariantCulture, out end)) continue;
                    this.ranges.Add(new Range(start, end));
                }
                this.ranges.TrimExcess();
            }
            public void Dispose()
            {
                var tmp = Connection;
                Connection = null;
                if (tmp!= null)
                {
                    try { tmp.Dispose(); }
                    catch { }
                }
            }
        }

        private RedisCluster(ClusterNode[] nodes)
        {
            this.nodes = new List<ClusterNode>(nodes);
        }
        private readonly List<ClusterNode> nodes;

        /// <summary>
        /// Attempt to connect to a redis cluster using a known configuration of one-or-more nodes;
        /// the nodes will be contacted to establish the actual cluster configuration.
        /// </summary>
        /// <param name="configuration">A comma-delimited sequence of nodes and options, in the same format as ConnectionUtils</param>
        /// <param name="log">Optionally record the steps taken during connection</param>
        /// <returns>A new cluster instance if possible, or null if it was not possible to connect to the cluster</returns>
        public static RedisCluster Connect(string configuration, TextWriter log = null)
        {
            var nodes = ConnectionUtils.ConnectToCluster(configuration, log);
            if (nodes == null || nodes.Length == 0) return null; // nothing available!

            return new RedisCluster(nodes);
        }

    }
}
#endif